She is a very kindhearted girl who comes from a wealthy family, she has shown she is not at all bothered by her condition. Unlike her father and sister, she does not blame jousting for her condition and still enjoys it as shown when she talked to Takahiro Mizuno about matches that were well-known.

She has a shy side as well, as she was seen blushing at Takahiro's compliment on her doing a good job in the garden and was this way again after accidentally grabbing his hand.

When she was young, Mireille was injured in a jousting accident and was rushed to hospital by her father who was there for her the whole time, the surgery was performed. Mireille's operation was done successfully and she was expected to recover, she strangely did not show any signs of getting better.

Her father was deeply affected by her injury and took his grief out on jousting and destroyed a statue of himself jousting, becoming truly disgusted with the sport for hurting his daughter. Her sister Noel blamed herself for being careless, as her sister was forced to spend her life in a wheelchair. Noel attempted to give up the sport but Mireille implored her to continue as she didn't blame her for the event. Mireille told her sister to continue while she supported her all the way in her endeavors in jousting to which the latter promised to make Mireille happy.